Olive
Olea europaea
Family: Oleaceae
Olives have been used for both their fruits and the oil produced from them for thousands of years. They appear throughout written history, used for religious and cultural purposes. The oil was first used by the Assyrians to light torches and for religious ceremonies.
Fossil evidence indicates the olive tree had its origins 20–40 million years ago in the Oligocene, in what now corresponds to Italy and the eastern Mediterranean Basin. Around 100,000 years ago, olives were used by humans in Africa, on the Atlantic coast of Morocco, for fuel and most probably for consumption. Wild olive trees, or oleasters, have been collected in the Eastern Mediterranean since ~19,000 BP. The genome of cultivated olives reflects their origin from oleaster populations in the Eastern Mediterranean. The olive plant was first cultivated some 7,000 years ago in Mediterranean regions.
The Spanish colonizers brought the olive tree to our region, and when anglos began to settle here, they had relatively little experience with them. Their cultural disconnection with the plant led to demonizing them as messy, and complaining that their pollen production (though no different than oaks, conifers, and many other wind pollinated plants) is too much. Ironically, when people moved here for the clean air, especially those with severe allergies, asthma, and tuberculosis, there were MORE olive trees in the region. There was also a public policy in the middle of the 20th century to “anglicize” the landscape—a racist policy that looked to replace the more “Mexican” neighborhoods and landscapes with more “modern” landscapes influenced by popular plants in the trade.
Technically, olive trees are banned in Pima County (they were banned in the 80s along with mulberries and Bermuda grass). This ban should be, and may soon be lifted. It is a shame that such a prolific, desert-adapted plant with so much potential should be targeted for air quality, while the abandoned lots and land clearing that really hurts air quality goes unchecked.
DESCRIPTION
Olives are tough trees that typically can reach about 30’ tall, though many cultivars top out at 15’ or less. They are evergreen with tough, sculptured trunks. If olives get steady care, they are moderately fast growing trees. They can be slow, when not given as much care, though they will survive. Having more than one tree is a good idea, as they fruit better with some cross pollination. Flowers occur in spring, and fruits develop over the warm season. Olives are mature when they reach their full color. At this time they are ready to drop from the tree. Depending on the cultivar, olives are picked unripe and green for eating or fully ripe for eating or oil.
USES & PRESERVATION
Most home gardeners are going to cure olives in one of the many ways they are cured:
Water Curing: each olive is cracked and soaked in daily changes of water for a week or more, then placed in a finish brine with salt and other flavoring elements. This is how Kalamata and Mediterranean-style cracked olives are done.
Brine Curing: olives are cured with salt from the beginning. This is how Greek black olives and Sicilian Green styles are accomplished.
Salt Curing: packing in salt for a month or more, then adding flavoring elements. This produces the drier, salt cured olives that are often packed in a little bit of oil.
Lye Curing: using 100% sodium hydroxide with no additives, a method that takes a few days. Spanish style green olives are cured this way.
Pressing Olive Oil at Home: it can be done. You need to obtain an olive oil press. And it takes a lot of oil and a lot of work to make just a little bit of oil, but the flavor is out of this world.
GROWING
Olive trees are easy to grow. They prefer full sun, and once established low to moderate water. Ideally, watering plants once to twice a month (depending on depth of watering and soil) is ideal in the warm season. If it does not rain in winter, water maybe once a month.
Olive trees are better adapted to poor soil than most other fruit trees and seldom suffer nutritional deficiencies. In residential settings, fertilization is unnecessary, even for a good fruit crop. But if you suspect your soil is devoid of any organic material, you can feed once a year with a general purpose organic fertilizer.
Avoid pruning, and just give these trees room to grow.
A mature tree can survive temperatures down to 15 degrees Fahrenheit for a limited amount of time; sustained cold below 15°F can be fatal—but this is something that almost never happens in our region.
As mentioned above, having more than one tree is best for fruit production—olives like cross pollination.
COMMON OLIVE VARIETIES
Arbequina From Spain, high oil content with a mild oil flavor, self-fruitful, very slow growing to 10-15' high. A little more tender than other olives, hardy to 25°F.
Manzanillo/Manzanilla From Spain, a green table olive, high pulp to pit ratio, buttery texture, pit separates easily, self-fruitful, grows 8-10' high.
Mission Recognized as an American cultivar that evolved from the Cornicabra olive brought over from Spain by missionaries. Self-fruitful, often picked ripe and dry salt cured to produce black olives.
Arbosana Grown as a complement to Arbequina, this variety has a more robust flavor than Arbequina. A compact grower that is moderately frost hardy. Fruit matures about 3 weeks later than Arbequina. Self-fruitful but produces higher yields with a pollenizer such as Arbequina.
Koroneiki This Greek variety is known for its peppery flavor. Used mainly as a blending varietal, its frost tenderness makes it more suitable for milder climates. Self-fruitful but produces higher yields with a pollenizer such as Arbequina or Arbosana.
Pendolino The Pendolino olive is used mainly as a pollenizer in Tuscany, but for landscaping Pendolino offers many desirable characteristics such as good cold hardiness and a dense, weeping canopy. It flowers early and profusely with a long bloom. Best paired with another variety. Produces a moderate amount of good quality oil with a very mild flavor, low bitterness and delicate pungency.
Swan Hill A fruitless olive tree used as an ornamental. Hardy to 15°F.